BIOL 3103 Exam 1 Study Guide: Introductory Material, Body Scaling, & Feedback Loops (Krogh, Bergmann, Membranes, Neurons, Senses, Vision)

Flashcards cover key terms and concepts from the notes across Introductory material, body scaling, feedback loops, biomolecules, membranes, neurons, synapses, senses, and vision. Each card provides a concise definition suitable for quick study.

Krogh’s principle

For every biological problem, there is an organism best suited to study it.

Bergmann’s rule

Animals in colder climates tend to be larger; warmer climates tend to have smaller bodies.

Body size vs complexity

Larger organisms require more complex transport systems due to lower surface area–to–volume ratio.

Surface area to volume ratio

SA scales with L^2 and V with L^3; larger animals have relatively less surface area for exchange.

Maximizing surface area adaptations

Flattening, branching, and folding (e.g., villi, alveoli, leaves) increase surface area for exchange.

Negative feedback

A control system that stabilizes a variable (e.g., thermoregulation) by counteracting changes.

Positive feedback

A control system that amplifies a response, driving the system away from the set point.

Feedforward control

Anticipatory responses that prepare the system for expected changes.

Antagonistic control

Opposing systems (e.g., sympathetic vs parasympathetic) that balance physiological states.

Sensor‑integrator‑effector

Core components of a feedback system: sensor detects, integrator processes, effector acts.

Carbohydrates

Biomolecule class: energy (glucose), storage (glycogen), and structural (cellulose) roles.

Lipids

Biomolecule class: membranes (phospholipids), energy storage (triglycerides), signaling (steroids).

Proteins

Biomolecule class: enzymes, transport, structural roles, receptors.

Nucleic acids

Biomolecule class: DNA stores information; RNA guides protein synthesis.

Fluid mosaic model

Dynamic phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

Passive transport

Diffusion, facilitated diffusion, and osmosis; no direct energy input.

Active transport

Movement of substances against gradients via energy input (primary/secondary).

Bulk transport

Vesicle-mediated processes like endocytosis and exocytosis.

Diffusion

Movement of molecules from high to low concentration by random motion.

Facilitated diffusion

Diffusion via membrane proteins that assist molecule passage.

Osmosis

Diffusion of water across a semipermeable membrane.

Primary active transport

Active transport powered directly by ATP (e.g., ion pumps).

Secondary active transport

Active transport driven by ion gradients established by primary pumps.

Endocytosis

Bulk transport into the cell via vesicle formation.

Exocytosis

Bulk transport out of the cell via vesicle fusion with the membrane.

Signal amplification

One ligand triggers many second messengers, increasing the response.

Second messengers

Molecules that relay signals inside the cell: cAMP, IP3/DAG, Ca2+.

cAMP

A cyclic nucleotide second messenger involved in many signaling pathways.

IP3/DAG

Second messengers produced from PIP2 that activate Ca2+ release and PKC, respectively.

Ca2+ as a second messenger

Calcium ions propagate intracellular signaling and trigger vesicle fusion.

Osmolarity

Solute concentration of a solution, irrespective of the type of solute.

Tonicity

Effect of a solution on cell volume due to osmotic differences.

Electrochemical gradient

Driving force for ion movement: combination of electrical and chemical gradients.

Equilibrium potential (Nernst)

Ion-specific voltage where there is no net ion flow for that ion.

Membrane potential (GHK)

Voltage across the membrane calculated from the weighted permeabilities of all permeant ions (Goldman–Hodgkin–Katz).

Resting membrane potential

Baseline Vm typically around −70 mV in many neurons.

ENa

Equilibrium potential for sodium ions (about +60 mV with typical gradients).

EK

Equilibrium potential for potassium ions (about −90 mV with typical gradients).

ECl

Equilibrium potential for chloride ions (about −65 mV).

ECa

Equilibrium potential for calcium ions (about +120 mV).

Neuron as RC circuit

Neuron membrane modeled as a capacitor with resistors (ion channels) in parallel.

Time constant (τ)

Tm = Rm × Cm; determines how quickly a membrane responds to stimuli.

Graded potentials

Small, variable, decremental changes in membrane potential.

Action potentials

All-or-none, non-decremental spikes that travel without decreasing amplitude.

AP steps

Resting potential, threshold, Na+ influx (depolarization), K+ efflux (repolarization), hyperpolarization, return to rest.

Refractory periods

Absolute (Na+ channels inactivated) and Relative (strong stimulus needed).

Myelination

Wrapping of axons by myelin to insulate and speed conduction.

Saltatory conduction

Rapid AP conduction jumping between nodes of Ranvier.

Nodes of Ranvier

Gaps in myelin where ion exchange occurs to regenerate APs.

Conduction speed factors

Faster with larger axon diameter and more myelination.

Synapses (electrical vs chemical)

Electrical: direct ionic current via gap junctions; Chemical: neurotransmitters across synaptic cleft.

Ca2+ triggering SNARE fusion

Calcium triggers vesicle fusion through SNARE proteins to release neurotransmitter.

SNARE complex

Protein complex (including synaptobrevin, SNAP-25, syntaxin) mediating vesicle fusion.

Post-synaptic receptors (ionotropic vs metabotropic)

Ionotropic: fast, ligand-gated ion channels; Metabotropic: slower, G-protein–coupled receptors.

Temporal summation

Integration of multiple stimuli over time at a neuron.

Spatial summation

Integration of stimuli arriving at different locations on the neuron.

Afferent vs efferent

Afferent: signals toward CNS; efferent: signals away from CNS.

Nerve, ganglion, nucleus

Nerve: bundles of PNS axons; ganglion: PNS neuron cell bodies; nucleus: CNS neuron cell bodies.

Decussation

Crossing over of neural pathways to the opposite side.

White matter vs gray matter

White matter: myelinated axons; gray matter: cell bodies and synapses.

Rostral vs caudal

Rostral: toward the front/anterior; caudal: toward the back/posterior.

Distal vs proximal

Distal: farther from the point of origin; proximal: closer to the point of origin.

Lateral vs medial

Lateral: toward the side; medial: toward the midline.

Autonomic nervous system

Controls involuntary functions via sympathetic and parasympathetic branches.

Sympathetic nervous system

Thoracolumbar; short preganglionic, long postganglionic; postganglionic NE.

Parasympathetic nervous system

Craniosacral; long preganglionic, short postganglionic; postganglionic ACh.

Nicotinic receptors

Ionotropic cholinergic receptors on the postganglionic neuron and at neuromuscular junction.

Muscarinic receptors

Metabotropic cholinergic receptors in various organs.

Cholinergic receptors

Receptors activated by acetylcholine (nicotinic and muscarinic).

GPCRs vs ion channels (taste signals)

Sweet/bitter/umami use GPCRs; salty/sour use ion channels.

Taste modalities

Five tastes: sweet, salty, sour, bitter, umami.

One taste cell per receptor type; one taste bud with multiple cell types

Each taste cell expresses one receptor type; taste buds contain several cell types.

Olfaction basics

Receptors in the nasal epithelium; axons project to glomeruli; odor detection via combinatorial coding.

Vision anatomy overview

Eye components: cornea, lens, retina, fovea, optic disc, optic nerve.

Rods vs cones

Rods: low-light vision; cones: color and high-acuity vision.

Phototransduction

Light activates rhodopsin, lowers cGMP, closes Na+ channels, causing hyperpolarization.

On/Off ganglion cells

Ganglion cells that respond to light/dark edges for edge detection.

Optic chiasm

Point where optic nerve fibers cross, enabling binocular vision.

UV/IR detection

Not detected by human photopigments; wavelengths outside their absorption.

Tapetum lucidum

Reflective layer in some animals that enhances night vision.

Basilar membrane in hearing

Structure in the cochlea that encodes pitch by location of hair cell deflection.

Hair cells

Mechanosensors in the inner ear that transduce sound into neural signals.